A wide variety of absorbent catamenial tampons have long been known in the art. Most commercially available tampons are substantially cylindrical in shape prior to use in order to facilitate vaginal insertion. It is well known that the vaginal canal is not smooth and linear, but rather is very contoured. Some digital tampons have tapered insertion ends to make insertion more comfortable. Others have flared withdrawal ends, presumably to provide a larger surface area for the user to push against during insertion. Nevertheless, the inventors of the present invention recognize that comfort and/or ease of the insertion of tampons is an important unmet consumer need. It is also important to have a tampon which is comfortable once inside the contoured vaginal canal. Additionally, it is desirable that the features rendering a tampon comfortable and/or easy to insert do not compromise, and alternatively even enhance the fluid acquisition capabilities of the tampon in use. Therefore, there is a need for new and improved comfortable shaped tampons. The shaped tampon aids in the insertion ease and/or comfort.
During the tampon production process, it is known that after the compression process that affords the tampon with its final shape, the tampon pledget tends to re-expand to its original dimension. To overcome this tendency, heat-setting has been utilized. The application of heat is designed to “set” the tampon in its compressed state. Conventional heat-setting, has some distinct disadvantages. First and foremost of these is the substantial increase in manufacturing time necessary to subject the tampons to an amount of heat necessary to obtain some level of set. If relatively high temperatures are used in an attempt to speed the process, the outside of the tampon which is a dense, compacted material is heated substantially faster than the inside, and the outer surface may be degraded and lose its absorbent characteristics.
Additionally, conductive heating methods typically do not uniformly stabilize the tampon and can result in the alteration of absorbent qualities in the outer layer of the tampon, as the outside of the tampon can dry more quickly than the inside. Conductive heating methods can also be time and energy intensive, as the air within the tampon must be heated, to dry the fibers via conduction from outside the tampon to the inside. Furthermore, high temperatures that could decrease cycle times cannot be utilized in conductive heating methods. The high temperatures may be above the melting point of portions of the tampon, such as the overwrap, which can result in a melted product.
While microwave heating can be a faster method of stabilizing tampons than conductive heating, only a small fraction of the outputted energy used in microwave heating is actually utilized to stabilize the tampon. As a result of this inefficiency, the energy costs of this method are relatively high.
Non uniform electric fields within a microwave oven can cause uneven heating of tampons. The shape of the resonating electric field is a pattern of high and low electric field intensity spots inside the microwaving oven. These spots are caused by standing waves. Standing waves arise due to the interactions that take place between electromagnetic waves bouncing back and forth in the microwaving oven when they are superimposed on one another. The result in this case is a checkered pattern of high and low electric field intensity spots that occurs in the microwaving oven. An exemplary uneven field distribution of microwave energy is shown in FIG. 13). The uneven heating of the tampon results in uneven shape stability of the finished product, an inconsistent consumer experience, and inconsistent product performance.
As such, it would be desirable to provide a method for stabilizing tampons via microwave energy that enables sufficient shape stability without the drawbacks from uneven heating.